+/* forward */
+static ir_node *transform_node(ir_node *n);
+
+/**
+ * Optimize (a >> c1) >> c2), works for Shr, Shrs, Shl
+ */
+static ir_node * transform_node_shift(ir_node *n)
+{
+ ir_node *left;
+ tarval *tv1, *tv2, *res;
+ ir_mode *mode;
+ int modulo_shf, flag;
+
+ left = get_binop_left(n);
+
+ /* different operations */
+ if (get_irn_op(left) != get_irn_op(n))
+ return n;
+
+ tv1 = value_of(get_binop_right(n));
+ if (tv1 == tarval_bad)
+ return n;
+
+ tv2 = value_of(get_binop_right(left));
+ if (tv2 == tarval_bad)
+ return n;
+
+ res = tarval_add(tv1, tv2);
+
+ /* beware: a simple replacement works only, if res < modulo shift */
+ mode = get_irn_mode(n);
+
+ flag = 0;
+
+ modulo_shf = get_mode_modulo_shift(mode);
+ if (modulo_shf > 0) {
+ tarval *modulo = new_tarval_from_long(modulo_shf, get_tarval_mode(res));
+
+ if (tarval_cmp(res, modulo) & Lt)
+ flag = 1;
+ }
+ else
+ flag = 1;
+
+ if (flag) {
+ /* ok, we can replace it */
+ ir_node *in[2], *irn, *block = get_nodes_block(n);
+
+ in[0] = get_binop_left(left);
+ in[1] = new_r_Const(current_ir_graph, block, get_tarval_mode(res), res);
+
+ irn = new_ir_node(NULL, current_ir_graph, block, get_irn_op(n), mode, 2, in);
+
+ return transform_node(irn);
+ }
+ return n;
+}
+
+